As disclosed in Patent Document 1, a sensor is conventionally known that detects the amount of particulate matter (hereinafter may be referred to as PM) in exhaust gas of an internal combustion engine. The sensor disclosed in Patent Document 1 includes an insulation layer on which the PM is to be deposited, and a pair of electrodes which are disposed on the insulation layer with those positioned apart from each other. When the sensor comes into contact with the exhaust gas so that the PM in the exhaust gas is accumulated between the electrodes, electrical conductivity between the electrodes changes in accordance with the amount of accumulated PM, thereby changing the resistance between the electrodes. Therefore, when changes in the resistance between the electrodes are detected, the amount of PM accumulated between the electrodes is detected. Thus, the amount of PM in the exhaust gas is estimated.
When the amount of accumulated PM exceeds a certain value, the resistance value between the electrodes does not change anymore so that the sensor is no longer able to generate an output value in accordance with the amount of 1, accumulated PM. A technology disclosed in Patent Document on the other hand, performs a PM reset by heating the sensor for a predetermined period of time with a heater built in the sensor to burn and eliminate the accumulated PM when the amount of accumulated PM is increased.